Method of smelting titaniferous iron ore



- Feb. 6, 1962 T. F. REED 3,020,150

METHOD OF SMELTING TITANIFEROUS IRON ORE Filed May 26, 1959 INVENTOR THOMAS F. REED uitornev trite; Sttes This invention relates to a method of smelting titaniferous iron ore.

Large quantities of titaniferous iron ore are available throughout the world, which ores are not commonly used to produce pig iron because of the difficulties encountered in smelting them. As little as 1% of titanium in an iron ore is sufficient to make the ore difficult to smelt in a blast furnace. The difficulties encountered in the process of smelting titaniferous iron ores are:

(1) An extremely viscous slag is obtained which is diificult to handle in flushing or casting slag.

(2) Accretions tend to form on the walls of the furnace hearth so that the furnace must be shut down periodically to remove the accretions.

(3) The hot metal tends to skull in the ladle more readily than hot metal obtained by smelting non-titaniferous ores.

Many attempts have been made to overcome the difiiculties connected with the smelting of titaniferous iron ores, but most of these attempts were based on the addi tion of a material to the slag to increase its fluidity. Such attempts have not proved successful.

It is therefore an object of my invention to provide a method of smelting titaniferous iron ores which is free of the difficulties mentioned above.

This and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a schematic sectional view of the bottom portion of a blast furnace incorporating my invention therein; and

FIGURE 2 is a view taken on the line lI-II of FIG- URE 1.

Referring more particularly to the drawings the reference numeral 1 indicates the crucible of a blast furnace. An iron notch 2 is provided in the wall 3 of the furnace in the usual manner adjacent the bottom thereof. Tuyeres 4 are provided through the wall of the furnace above the iron notch in the usual manner. As shown, the tuyeres 4 are located at a level at the top of the crucible but they may also be located at the bottom of bosh 5. The parts so far described and the remaining part of the furnace not shown are conventional. Attention is directed to the seventh edition of The Making, Shaping and Treating of Steel, published by United States Steel Corporation for further description.

According to my invention a plurality of slag notches 6, 7 and 8 are provided at different elevations between the iron notch 2 and the tuyeres 4. As shown, slag notch 7 is located diametrically opposite the iron notch 2 and slag notches 6 and 8 are located to each side thereof but within an arc of 45 on each side of diameter 9.

The notch 6 is at the lowest level, notch 7 at a second level and notch 8 at the highest level. If only two slag notches are provided, one will be on each side of the diameter 9 and as close to the diameter 9 as possible. Another feature is that the slag notches are constructed in the same manner as the iron notches and not in the same manner as the slag notches previously used which incorporate water coolers.

In carrying out my method the blast furnace is charged atent and the iron smelted in the usual manner. The main feature of my method is a change in the flushing practice. In prior practice and in practices used with nontitaniferous iron ores, the furnace is cast at regular intervals with the furnace being flushed once between casts about one hour before each cast. In such practice pig iron is not normally removed in the flush, and therefore slag may be present on top of the molten pig iron when the furnace is cast. According to my invention the molten pig iron is allowed to accumulate until it reaches the level of the slag notch. The furnace is then flushed to remove the molten slag that forms above the iron, and the furnace then cast as soon as possible but in no case more than 45 minutes after the finish of the flush. In most cases some pig iron will be removed during the flush to ensure that all of the slag is removed from the furnace at this time. It is for this reason that the slag notch must be made in the same manner as the iron notch.

The preferred method of carrying out my invention, especially in a blast furnace of ordinary construction, involves permitting the molten pig iron and slag to accumu late in the furnace until a substantial amount of slag is above the level of the slag notch, and then flushing the furnace to remove the slag. A final flushing is then made when the iron has accumulated above the slag notch, after which the furnace is cast as soon as possible. 'If necessary, more than one intermediate flush may be made. If the intermediate flush is omitted, the furnace would have to be tapped more frequently than is common, since otherwise the slag would reach the level of the tuyeres. One way of increasing the time between casts would be to raise the level of the tuyeres, but this is generally not advisable for various reasons. Since my method requires that the molten iron at least reach the level of the slag notch before tapping, whereas other practices used with common iron ore do not have such a requirement, the provision of the plurality of the slag notches permits the operation of the furnace to be tied in with the requirements of the entire blast-furnace and open-hearth shops, particularly when the furnace has been off blast for any reason. In other words, the slag may be normally flushed through either slag notches 7 or 8, but in some cases the blast will have been shut off for a period of time which permits the molten iron only to reach the level of slag notch 7 when the time the furnace should be cast arrives. Under this condition the flushing will be through notch 6. In flushing the slag notch is opened with an oxygen lance, the hot metal and slag is drained from the furnace through a runner and collected in one or more receptacles. The wind rate is reduced, the notch replugged and the wind rate restored to normal.

In order to keep as much titanium as possible out of the molten metal I prefer to maintain a low smelting temperature. This is done by maintaining the slag-basicity ratio CaO+MgO/Si0 between 1.0 and 1.5 and the silicon content of pig iron between 1.8 and 50%. In general, the slag-basicity ratio is high when the silicon content is low and the slag-basicity ratio low when the silicon content is high." For example, if the slag-basicity ratio is between 1.4 and 1.5 the hot metal silicon percentage is preferably held between .50 and and if the slagbasicity ratio is between 1.0 and 1.2 the silicon content is preferably-held between 1.3 and 1.8%. This control can be readily elfected by varying the hot blast temperature, the coke rate or the amount of ilme added to the furnace.

Titaniferous iron ore, as used in the specification and claims, means metal ore, sinter or any material of the same composition regardless of its form. While the practice may vary as is common in smelting of iron ore, an

3,o2o,i5o 3 4 experimental blast furnace was operated according to the (4) Slag analysis (typical), percent: following practice: :(a) SiO 32.92 (b) A1 12.94 VARIABLES (c) CaO 31.46 (1) Burden ratio, lbs. ore/lbs. coke 1.80 to 1.90 (d) MgO 16.56 (2) Basicity ratio: (e) TiO 4.42 (a) Ca0+MgO/Si0 1.40to 1.50 (1) Mn 0.23 (b) CaO+MgO/SiO +Al O 1.00 to 1.10 -(g) Fe 0.87 (3) Materials charged to furnace per day: (h) S 1.11

(a) Titaniferous iron-ore (i) Balance impurities.

Smter. "g to While one embodiment of my invention hasbeen shown (b) 6 1200 and described, it will be apparent that other adaptations Llmestqne to and modifications may be made without departing from Dolomlte 5,000 to 5,500 h scope of the fonowing claims (e) Gravel lbs 1,700 to 1,900 I claim, (4) Wind rate c.f.m 800 p Hot blast tempamture a F" 1,000 to 1,150 1. The method of smelting titamferous iron ore which (6) Blast-furnace top pressure Essentially atmospheric (7) Size analysis of materials:

(a) Titaniferous iron-ore sinter- Plus 1 inch percent 1.4 Plus /2 inch -1 d0 12.5 Plus 3 mesh ..do 46.0 Plus 10 mesh do 85.2 Plus mesh do. 920

(b) Coke sized to 1% inches by 1 inch (0) Limestone sized to 2% inches by inch (d) Dolomite sized to 1% inches'by inch (2) Gravel 33% plus /2 inch, 82% plus 3 mesh,

97% plus 10 mesh.

(8) Chemical analyses of raw materials, percent When the experimental furnace was operated according to the above practice with casts every 3 hours and flushes minutes before each cast the following results were obtained:

(1) Production rate 24,660 to 26,660 lb. pig

iron per day (2) Coke rate 1,540 to 1,740 lb. per ton of hot metal (3) Metal analysis, percent:

(a) Fe 94.9 to 96.9 ([2) Si 0.40 to'0.60 (c) S 0.08 to 0.14 (d) Ti 0.07 to 0.15 (e) C 3.10to3.89

(1) Balance, V, Mn, P, and other impurities.

comprises charging a blast furnace having a slag notch, operating the blast furnace to form molten pig iron having a low titanium content and slag having a large silicon content as compared to the titanium content, permitting the molten pig iron and slag to accumulate in the furnace until the molten pig iron reaches the level of the slag notch, flushing the furnace to remove all the molten slag, then casting the molten pig iron from the furnace Within 45 minutes after the finish of the flush, continuing operation of the furnace to'produce more molten pig iron, and repeating the flushing and casting operations in the manner set forth above.

2. The method of smelting titaniferous iron ore according to claim 1 in which a low smelting temperature is obtained by maintaining a slag-basicity ratio between 1.0 and 1.5 and between 1.8 and 0.5 percent silicon in the pig iron, the low slag-basicity ratios being used with the high silicon contents and the high slag basicity ratios with the low silicon contents.

3. The method of smelting titaniferous iron ore which comprises charging a blast furnace having a slag notch, operating the blast furnace to form molten pig iron having a low titanium content and slag having a large silicon content as compared to the titanium content, permitting the molten pig iron and slag to accumulate in the furnace until a substantial amount of slag is above the level of the slag notch, flushing the furnace to remove at least part of the molten slag, then permitting molten iron and slag to accumulate in'the furnace until the molten pig iron reaches the level of the slag notch, flushing the furnace to remove all the molten slag, then casting the molten pig iron from the furnace within 45 minutes after the finish of the flush, continuing operation of the furnace to produce more molten pig iron, and repeating the flushing and casting operations in the manner set forth above.

4. The method of smelting titaniferous iron ore according to claim 3 in which a low smelting temperature is obtained by maintaining a slag-basicity ratio between 1.0 and 1.5 and between 1.8 and 0.5 percent silicon in the pig iron, the low slag-'basicity ratios being used with the high silicon contents and the high slag-basicity ratios with the low silicon contents.

References Cited in the file of this patent UNITED STATES PATENTS 417,691 Wainwright Dec. 17, 1889 486,941 Rossi Nov. 29, 1892 1,092,168 Prudhomme Apr. 7, 1914 1,664,832 Power et a1 Apr. 3, 1928 1,868,694 Coghlan July 26, 1932 1,889,160 Strain et a1 Nov. 29, 1932 2,471,242 Royster May 24, 1949 

1. THE METHOD OF SMELTING TITANIFEROUS IRON ORE WHICH COMPRISES CHARGING A BLAST FURNACE HAVING A SLAG NOTCH, OPERATING THE BLAST FURNACE TO FORM MOLTEN PIG IRON HAVING A LOW TITANIUM CONTENT AND SLAG HAVING A LARGE SILICON CONTENT AS COMPARED TO THE TITANIUM CONTENT, PERMITTING THE MOLTERN PIG IRON AND SLAG TO ACCUMULATE IN THE FURNACE UNTIL THE MOLTEN PIG IRON REACHES THE LEVEL OF THE SLAG NOTCH, FLUSHING THE FURNACE TO REMOVE ALL THE MOLTEN SLAG, THEN CASTING THE MOLTEN PIG IRON FROM THE FURNACE WITHIN 45 MINUTES AFTER THE FINISH OF THE FLUSH, CONTINUING OPERATION OF THE FURNACE TO PRODUCE MORE MOLTEN PIG IRON, AND REPEATING THE FLUSHING AND CASTING OPERATIONS IN THE MANNER SET FORTH ABOVE. 